Full coding of a Multimodal (Vision) Language Model from scratch using only Python and PyTorch.
We will be coding the PaliGemma Vision Language Model from scratch while explaining all the concepts behind it:
- Transformer model (Embeddings, Positional Encoding, Multi-Head Attention, Feed Forward Layer, Logits, Softmax)
- Vision Transformer model
- Contrastive learning (CLIP, SigLip)
- Numerical stability of the Softmax and the Cross Entropy Loss
- Rotary Positional Embedding
- Multi-Head Attention
- Grouped Query Attention
- Normalization layers (Batch, Layer and RMS)
- KV-Cache (prefilling and token generation)
- Attention masks (causal and non-causal)
- Weight tying
- Top-P Sampling and Temperature
and much more!
All the topics will be explained using materials developed by me. For the Multi-Head Attention I have also drawn all the tensor operations that we do with the code so that we can have a visual representation of what happens under the hood.
Repository with code and notes: https://github.com/hkproj/pytorch-paligemma
Prerequisites:
1) Transformer explained: https://www.youtube.com/watch?v=bCz4OMemCcA
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Chapters
00:00:00 - Introduction
00:05:52 - Contrastive Learning and CLIP
00:16:50 - Numerical stability of the Softmax
00:23:00 - SigLip
00:26:30 - Why a Contrastive Vision Encoder?
00:29:13 - Vision Transformer
00:35:38 - Coding SigLip
00:54:25 - Batch Normalization, Layer Normalization
01:05:28 - Coding SigLip (Encoder)
01:16:12 - Coding SigLip (FFN)
01:20:45 - Multi-Head Attention (Coding + Explanation)
02:15:40 - Coding SigLip
02:18:30 - PaliGemma Architecture review
02:21:19 - PaliGemma input processor
02:40:56 - Coding Gemma
02:43:44 - Weight tying
02:46:20 - Coding Gemma
03:08:54 - KV-Cache (Explanation)
03:33:35 - Coding Gemma
03:52:05 - Image features projection
03:53:17 - Coding Gemma
04:02:45 - RMS Normalization
04:09:50 - Gemma Decoder Layer
04:12:44 - Gemma FFN (MLP)
04:16:02 - Multi-Head Attention (Coding)
04:18:30 - Grouped Query Attention
04:38:35 - Multi-Head Attention (Coding)
04:43:26 - KV-Cache (Coding)
04:47:44 - Multi-Head Attention (Coding)
04:56:00 - Rotary Positional Embedding
05:23:40 - Inference code
05:32:50 - Top-P Sampling
05:40:40 - Inference code
05:43:40 - Conclusion